Lower-limb joint work symmetry responses to load carriage and prosthetic foot type during transtibial amputee walking

Individuals with lower-limb amputations are typically prescribed passive prosthetic feet for everyday walking. However, when carrying additional loads, users demonstrate increased reliance on their intact limb which can lead to overuse injuries. Powered prostheses have been shown to reduce compensations during unloaded walking, but their efficacy during load carriage remains unknown. Furthermore, how the position of an added load affects intact limb reliance is not well understood. This study determined (1) how the presence and placement of an added load affects between-limb joint work symmetry for individuals walking with transtibial protheses, and (2) how prosthetic foot type (passive or powered) affects joint work symmetry during load carriage. Kinematic and kinetic data were collected from unilateral transtibial prosthesis users (n = 12) wearing a passive or powered prosthesis while walking with no added load, a 13.6 kg load worn on the front of their torso, or the same load worn on their back. Work symmetry, calculated as the difference between intact-side and prosthesis-side net joint work, was determined for the ankle, knee and hip to quantify intact limb reliance. Ankle and hip work symmetry improved for the Front Load compared to the No Load condition, due to a tradeoff between intact ankle and intact hip demand. Furthermore, ankle work symmetry improved for all load conditions while wearing the powered prosthesis. These results highlight changes in compensatory strategies during different load carriage conditions and encourage the use of powered prostheses to reduce intact limb reliance during activities involving load carriage.